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DUNHAM EXPLORING GENETIC OPTIONS IN CATFISH
AUBURN, Ala.__--Rex Dunham, a fish geneticist working in the Alabama
Agricultural Experiment Station at Auburn University, has spent the
past 13 years trying to build a better catfish. The result has been
a foray into the world of genetic engineering that has yielded success
and international attention.
Dunham, who received the CFA Distinguished Service Award recently, earned
his B.S. degree in ecology, ethology and evolution from the University
of Illinois and his M.S. and Ph.D. degrees in fisheries and allied aquacultures
from Auburn. He joined the Auburn faculty in the Department of Fisheries
and Allied Aquaculture in 1981 where he has focused on improving the
growth and production of food fish, particularly catfish.
"Our overall program is to improve several traits in the catfish,"
said Dunham, an associate professor in the Department. "These include
growth rate, feed conversion efficiency, disease resistance, harvestability,
tolerance to low oxygen, decreased fat and changing the body shape to
get more meat and less waste."
When he first came to Auburn, Dunham joined a team of scientists that
had been working on a crossbred catfish project for many years. By 1988
he had helped produce the "super catfish," a hybrid catfish
developed by crossing female channel catfish with male blue catfish.
The "super catfish" grows faster, has higher survival rates,
needs less oxygen, has more edible meat and is easier to catch than
the traditional catfish varieties used by commercial producers. All
these characteristics mean higher profitability for the producer.
But hybridization is not the only area of genetics Dunham has investigated.
His work with transgenic fish, fish which have been implanted with genes
of other animals, has garnered attention, and some controversy, from
throughout the world.
Working with scientists at John Hopkins University, the University of
Maryland, and the University of Alabama at Birmingham, Dunham successfully
implanted growth hormone genes into both carp and catfish. The genes,
from rainbow trout and humans, were implanted by injecting the foreign
gene into the one-cell stage of fish embryo using a tiny micro-needle.
Analysis of the fish as they have hatched and matured has shown that
the implantation process works. The next step is to determine if the
gene can be transferred to the offspring of the host fish. Though other
phases of research have been accomplished in the lab, this step requires
that the fish be placed in ponds.
When Dunham applied for federal permission to place the transgenic fish
in a pond in 1986, a complicated process was set into motion which ended
recently with approval for the release.
The carp have already shown signs of more rapid growth in the laboratory
and Dunham is hopeful that the process will eventually lead to superior
catfish that can reach market size faster, be more disease resistance,
and have other beneficial characteristics for production aquaculture.
But, Dunham notes, this is only the beginning of a long and complex
research program. "We're talking years of research, still,"
he said.
Dunham was reared on a small farm in Illinois which had a farm pond.
His exposure to catfish in this pond, and the publicity that catfish
farming was receiving in 1976, led him to Auburn and into catfish genetic
research.
"Auburn has a multifaceted approach to improving catfish and uses
evaluation, selection, crossbreeding of channel catfish and hybridization
between species of catfish, and genetic engineering to improve their
commercial qualities," said Dunham. "Likely, the best fish
will eventually be produced using a combination of these breeding programs."
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By:
Katie Smith
June 18, 1991
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